Measuring operations are essential to any manufacturing process and are particularly critical in the mass production of precision machinery. In such processes, many measurimg steps are employed to ensure proper dimensional tolerances of a part and to provide for interchangeability of mass produced parts. Additionally, measuring steps are necessary for quality control, monitoring of manufacturing errors and assessment of wear in tooling, dies and the like.
One measuring operation which is required in many manufacturing steps involves profiling. By profiling is meant the measurement of the three-dimensional shape of a part and as particularly employed herein, cylinder profiling refers to the profiling of the bore hole of a cylinder to assess various properties such as straightens, cylindricity, taper and the maximum and minimum radius thereof. Many types of pumps, internal combustion engines, compressors and similar devices employ pistons which travel in cylinders and the manufacture of such devices is dependent upon the profiling of these cylinders to ensure proper fit of the pistons therein.
Heretofore, profiling of cylinders was a painstaking, manual process accomplished by the use of micrometers, calipers, and the like. Various attempts at automation of such measurements involved the use of gages adapted to measure a single point or single tier of points in a cylinder. Use of such tooling necessitated making a repeated series of measurements as the measuring gage was drawn through the cylinder bore. Such techniques are generally slow and inaccurate insofar as the measuring gage can be displaced during subsequent measuring steps.
U.S. Pat. No. 4,407,071 discloses a device for measuring internal diameters of pipes and includes a plurality of feeler fingers disposed in a circular array to measure the diameter of a cylinder in a particular, single plane. Measurement of the diameter of the entire cylinder involves making repeated measurements while drawing the apparatus therethrough. U.S. Pat. No. 3,075,292 discloses a gage for measuring the diameter of a well casing. The gage of the '292 patent is essentially an electronic caliper which is drawn through the tubing to measure the diameter at particular levels therein. Use of apparatus similar to those described does allow for profiling of cylinders; however, the implementation of the techniques involved is slow and complex and requires precise positioning and repositioning of the measuring gage to obtain an accurate profile of a cylinder. Therefore, apparatus of this type is not at all suited to high volume automated production processes.
Through the use of a fast, simple and accurate cylinder profiling technique, manufacturers could maintain high levels of quality control in a large volume production process so as to produce quality products; additionally, use of such techniques would allow for ready monitoring of tooling and die wear so as to minimize maintenance and down time of equipment. Despite the advantages which attach to the use of high volume profiling, manufacturers have not readily adopted such techniques owing to the fact that presently available equipment is expensive, difficult to operate, and frequently of inadequate accuracy. It will thus be appreciated that there is a need for a cylinder profiling gage which is accurate, simple and easy to use. It is further desired that such apparatus be readily adaptable to automated production and quality control techniques.
The present invention provides for a cylinder profiling gage which accurately profiles an entire cylinder bore substantially instantaneously without necessitating repositioning of a measuring unit within the cylinder. Furthermore, the gage of the present invention may be readily utilized by an unskilled worker to provide highly accurate data. The output of the gage of the present invention may be displayed in an operator-readable graphic form providing for rapid visual identification of cylinder characteristics. The output of the gage may also be provided in numerical form, either as a human-readable output or as machine-readable data which may be processed in accord with various statistical quality control protocols. These and other advantages of the present invention will be readily apparent from the drawings, description, discussion and claims which follow.